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Messrs. Editors.

ILL you permit a brief criticism of your selections for "The Popular Science Monthly"? My appreciation of the journal is sufficiently indicated in its reception and careful reading from the time it was begun. I have for some fifty years tried to do my own thinking—not so self-sufficiently, however, that I am not very glad to get what true help I can from other thinkers.

I have been attracted to "The Popular Science Monthly" by the evident desire and purpose of its conductors to give a fair hearing to all views, pro or con, on any subject of general scientific interest. There is one, however, now before the world which, in importance to the whole human family, can be assigned to no second place, which, in my view, you treat in a very partisan manner. I refer to the Harmonial Philosophy, Spiritualism, or whatever it may be called. This question, whether evolving truths of the deepest importance to humanity, or a species of insanity, delusion, or imposition, demands attention and discussion; for millions of people are to-day affected more or less by its phenomena and teachings, and it is spreading with a rapidity un-realized by the indifferent observer. From its first opening with the Fox girls near Rochester, New York, to the present, I have observed it closely, and often under very favorable circumstances. To endorse it en masse would to me be folly; to utterly ignore it, equally so.

I am fully satisfied that there are great and most important truths involved in the subject, which demand elimination from what may be accompanying rubbish. Now, when you select for "The Popular Science Monthly" articles all, or nearly so, on one side of this question, and from men like Hammond, Beard, Gairdner, Trowbridge, etc., you leave the path of true science for that of the partisan.

To me, as well as several other readers of the journal with whom I have communicated, a fair discussion of this subject would not only add interest, but remove a present offense. You might lose some bigoted and fossilized readers, but you would gain an equal if not larger number of the less prejudiced.

Messrs. Editors.

an article on "Wasted Forces" by William H. Wahl, Ph.D., in "The Popular Science Monthly" for July, 1879, I note some remarkable statements in that part of the article which deals with the efficiency of steam-engines. The writer seems to have ignored the principal cause of wasted heat in the steam-engine, viz., the efficiency of the fluid, and to have augmented the other losses in order, apparently, to account for the low efficiency of the whole machine. In doing this he has given figures, which not only leave wrong impressions in the minds of those not familiar with the subject, but he makes opportunities for improvement seem far greater in some directions than they are. I do not care to call in question the fifteen per cent, which Mr. Wahl gives as the greatest efficiency yet obtained from steam-engines, but in locomotive-engines, with which I am most familiar, five per cent, will more nearly represent the efficiency of average performance. Granting that fifteen per cent, may be obtained in the most economical engines, it is to Mr. Wahl's method of accounting for the loss of eighty-five per cent, that I object. On page 292 one reads: "For by far the greater portion of this eighty-five per cent, of wasted power is chargeable directly to the steam-boiler, and but a comparatively small proportion thereof to the engine." And again, on page 293: "Summing up all the items of loss in the steam-generator, it is probable that with the best forms of boiler which it has been possible to construct, not more than twenty-five per cent, of the theoretical thermal effect of the fuel is utilized in the generation of steam; and of this twenty-five per cent., from five to ten per cent, is lost somewhere on the passage of the steam from the boiler to and through the engine by condensation in steam-pipes, and friction of the machinery, leaving us but fifteen or twenty per cent, actually realized in practice." As a matter of fact I have repeatedly observed from fifty to fifty-five per cent, of the total theoretical number of heat-units obtainable from the complete combustion of bituminous coal transferred to the water and steam in the boiler from locomotive fire-boxes, in which the proper burning of coal is far more difficult than in stationary fire-boxes, or those with natural draught and ample room; in such fire-boxes as last mentioned, coal is